1. Field of the Invention
The present invention relates to a power saving technique of an information-processing apparatus always connected to the Internet.
2. Description of the Related Art
In recent years, battery-powered information-processing apparatuses such as notebook-sized personal computers and personal digital assistants (PDAs) have been variously developed. In this kind of information-processing apparatuses, various methods of controlling power saving are proposed to make long the lifetime of battery (e.g., Japanese Patent Application KOKAI Publication No. 6-149406).
Likewise, various methods of controlling power saving are proposed in desktop personal computers, that is, desktop information-processing apparatuses driven by an external power source (AC utility source) (e.g., Japanese Patent Application KOKAI Publication No. 7-134628). In this case, constant connection to the Internet is taken into consideration.
Recently, the development of an information-processing apparatus called a home server has been advanced. The home server includes a tuner for receiving terrestrial broadcasting and satellite broadcasting, a router for making connection with the Internet. In addition, the home server has a function of making wireless communication with many electronic apparatuses in the home. One home server is located in the home, and thereby, the following matters are possible. For example, members of the family can set a video cassette recorder to record a program in advance while they are in an individual private room. Members of the family can appreciate the recorded television broadcasting on the display of their own terminal. Members of the family can browse Web pages published on Internet using the display of their own terminal. The power saving control described above is applied to the home server, and thereby, wasted power consumption can be prevented.
In general, the home server requires maximum CPU power when carrying out so-called image processing. According to image processing, an encoder compresses and encodes video data of the television broadcasting received by the tuner, or a decoder decodes the compressed and encoded video data. On the other hand, when the router is operating, the CPU power is not required so much. Therefore, it is preferable to carry out finer power saving control considering the required CPU power.
However, according to the power saving control method, it is determined whether any device is operating or not, and the changeover of the CPU power is merely made between two ways, that is, on and off. For this reason, it is the actual state that wasted power consumption still occurs.